Currently, parents are allowed to keep the first £20 of child maintenance per week before their benefits are reduced. Once the full disregard is introduced, the income from child maintenance will not affect benefits at all.
The disregard and earlier changes to child maintenance are expected to lift 100,000 more children out of poverty.
Secretary of State Yvette Cooper said:
“We want to do more to help families to get by during the recession. This will mean that money meant for children actually goes to the children. And it will help families sort out their own extra payments too whenever they can, without getting tied up in benefit changes.
"This is one more step in our fight against child poverty as we move towards enshrining our commitment to eradicating child poverty by 2020 in legislation.â€
Chief Executive of single parent charity Gingerbread Fiona Weir said:
"Gingerbread welcomes the Government’s decision to allow children in the poorest families to receive the full value of any child maintenance paid by their non-resident parent.  In everyday terms, it will mean that every penny paid in maintenance goes to the child and is expected to lift thousands more children out of poverty.
"Child maintenance makes a real difference to children’s lives, helping to pay for basics such as shoes and nutritious food, and for important extras such as school trips."
The full disregard will encourage both parents to set up an effective maintenance arrangement and the non resident parent to pay maintenance because all of the money will go to the children rather than the state.